N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
if N==2:
  if sum(A)==sum(B):
    print(abs(A[0]-B[0]))
  else:
    print(-1)
else:
  a=sum(A)
  b=sum(B)
  if (a-b)%(N-2)==0:
    x=(a-b)//(N-2)
    for i in range(N):
      d=x-A[i]+B[i]
      if d<0 or d%2==1:
        print(-1)
        exit()
    print(x)
  else:
    print(-1)